Simulation of Kinetics

I am looking for a program that will run on an IBM-PC, Mac, or VAX
that will allow me to simulate the kinetic progress of reactions. The
reactions that I am interested in are nucleation/polymerization
reactions as in the case of actin, tubulin, etc.
The ideal program would allow me to type in a reaction scheme, and
rate constants, and would plot the progress of the reaction versus
time. Does such a program exist, and if so where can I obtain a copy.
Peter Prevelige
Dept. of Biology
MIT
Cambridge, MA. 02139
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